1. Field of the Invention
The present invention relates to an industrial machine with a mechanism capable of moving a ram in the Z-axis direction perpendicular to a base surface.
2. Description of Related Art
A typically known industrial machine is capable of a Z-axial movement of a ram held in a direction perpendicular to a base surface (see, for instance, Patent Literature 1: JP-A-2001-21303).
The industrial machine disclosed in Patent Literature 1 is a coordinate measuring machine. The coordinate measuring machine includes: column and support that are set perpendicular to the base surface and are movable in the Y-axis direction; a beam provided between ends of the column and support; a slider that are movable on the beam in the X-axis direction; and a ram that is provided to the slider in a manner movable in the Z-axis direction and has an end attached with a probe.
In the coordinate measuring machine, a scale is provided along each of the X-, Y- and Z-axes to define a measurement coordinate system using values read from these scales as a reference. The coordinate measuring machine monitors temperature environment and reconstructs the measurement coordinate system upon detecting a temperature change.
According to the arrangement of Patent Literature 1, even when the scale(s) suffers from a dimensional change due to thermal expansion, a highly accurate measurement can be performed. However, the arrangement is not effective when components other than the scales, such as the column, support and ram, are thermally expanded. Since such thermal expansion lowers, in particular, measurement accuracy in the Z-axis direction, measurement environment needs to be accurately controlled. For instance, when the coordinate measuring machine is switched on and then a master ball showing the origin point position of the measurement system is continuously measured with the probe, an increase in the temperature of a drive motor for driving a contact point causes the thermal expansion of the column, support and ram with resulting different dimensional change amounts. Thus, mainly a Z-axis value is shifted as compared with a value when the measurement is started upon switch-on and thus a Z-axis measurement accuracy is lowered. In order to prevent such a lowered Z-axis measurement accuracy, an industrial machine capable of accurately calculating the Z-shift amount of the ram resulting from thermal expansion has been desired.